Semiconductor wafers are used in applications such as electronics or optronics for example, especially to construct components and circuits on such structures. These wafers may be circular, with a diameter of for example 200, 300 or 450 mm, but they may also be substrates of other dimensions and shapes, such as for example rectangular panels for applications in the field of photovoltaics or displays (i.e., screens).
The surface quality of these wafers is an important parameter. This surface quality is characterized especially by a measure of roughness, which must be as low as possible. The roughness may be measured at various frequencies, high-frequency roughness characterizing variations of high spatial frequency of the surface state of the wafer whereas low-frequency roughness characterizes variations of lower spatial frequencies.
Several types of technique have been envisaged for improving this surface quality: planarization by mechanical or chemical means (or combinations thereof), thermal annealing (especially at high temperatures), etc. It has also been proposed that the surface of the wafers be exposed to pulsations of a radiation arising from a laser or from a microwave source. In this regard reference may be made for example to the document WO 2007/142911. This document proposes that a pulsed stream be applied to the surface of a substrate.
While WO 2007/142911 does disclose utility in reducing surface roughness, there still remains a need for improvements in such processing. The present invention now provides a practical improvement of the known techniques for decreasing the roughness of semiconductor wafers.